the 'O' ring is fine it's the clear rubber seal that distorts and creates a bubble inside that centre hole...

Bit of an update.. so to be able to drive it off boost, I disconnected the waste gate and set it up so that it was always open, and thought it should be alrite to drive, half way to work it started to play up (flat spot) but this time it was dieing at about quater throttle, when I got to work I hooked up me timing light, just to check if it was loosing spark, It has good solid spark even when the flat spot appears, So now i'm thinking it may be the TPS? Is this somthing a fulty TPS would do?